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thickets along the river-banks. This list must be regarded 
as an experiment. It is based on all the sources of infor- 
mation which have been available to me. The most impor- 
tant of these are: BuNGE’s Reliquiae Lehmannianae, Madame 
FEDTSCHENKO’S and Boris FEDTSCHENKO’S various works, 
Lipsky’s systematic memoirs in Acta Horti Petropolitani, 
Litwinow’s descriptions some in the schedules to Herbarium 
florae Rossicae, others in “Travaux de la Musée de l’Aca- 
démie”, and finally it is based on my own collections. 
Two great difficulties had to be contended with in com- 
posing the list. First the records of occurrence in the various 
memoirs are not always sufficiently exact to allow of an 
accurate determination as to whether the plant in question 
occurs on the territory dealt with in this work, or north of 
our selected boundary, or on the mountains to the east or 
south of it; secondly it is difficult to determine the limits of 
any particular species in a flora which is still insufficiently 
investigated. I have therefore adopted a somewhat broad 
outlook as regards this question and have therefore excluded 
several “minor species” described in recent years by WINKLER, 
Lırwınow and others. The synonymy also presents difficul- 
ties which, however, I hope have been surmounted in most 
cases. 
I am fully aware that the list as such has many defic- 
iencies, but hope that it may serve the purpose for which 
it has been prepared, namely to give fairly accurate infor- 
mation about the growth-forms of the desert. 
. Ås regards the growth-forms I have chosen the system 
proposed by RAUNKIÆR, partly because, in spite of its one- 
sidedness, it emphasises one of the most important features 
of plant-life, also because it is easier to handle than other 
classifications of growth-forms, and finally because by using 
RAUNKIÆR'S system it is possible to express statistical data 
which may be compared with corresponding data for other 
regions. 
The biological types (growth-forms) of RAUNKIÆR (see 
Raunkier 1904, 1905, 1907) are arranged according to the 
way in which plants live through unfavourable seasons, and 
special emphasis is laid on the degree and kind of protection 
